Medicare's new prescription drug benefit is a good deal for seniors and taxpayers, President Bush said Tuesday, even as he acknowledged that the program got off to a rocky start when it began in January.

"Anytime Washington passes a new law, sometimes the transition period can be interesting," the president during a town-hall style conversation in upstate New York.

Bush was in town to promote Plan D, the new Medicare prescription drug plan that he said "makes a lot of sense" for the vast majority of seniors. Plan D allows private companies to design and sell insurance plans offering prescription drug coverage.

"If you're a low income senior, the government's going to pick up a significant portion of your tab," he said. "If you're an average income senior, you're going to see your drug bills cut in half. If you're a taxpayer, the anticipated costs are significantly lower than we thought.

"It's working," Bush said. "It makes a lot of sense."

But critics say sign-up has been slow because the elderly are bewildered over which of the private coverage plans to join. Some Democratic lawmakers on Tuesday proposed the sign-up deadline be extended to Dec. 31, the current deadline is May 15. They also want penalties waived for seniors who sign up late.

Those critics note large numbers of seniors couldn't get their drugs due to problems transferring coverage when the program started.

"Seniors should not be forced to pay the price for the president's confusing prescription drug plan," said House Minority Leader Nancy Pelosi. "Democrats are fighting to ensure that seniors do not have to pay the Bush prescription drug tax and are given enough time to navigate the complexities of a flawed plan, which was written for big pharmaceutical companies rather than everyday Americans who deserve a real prescription drug benefit."

Other lawmakers are promoting changes to the Medicare drug program that would allow the Department of Health and Human Services to negotiate lower prices for mass purchases of drugs through the Medicare program.

"The rapidly escalating price of prescription drugs threatens to undermine the very drug benefit Congress passed to deliver real savings to seniors," said Sen. Olympia Snowe, R-Maine, speaking on behalf of Sen. Ron Wyden, D-Ore. “Our amendment manages costs in a commonsense way — harnessing the buying power of millions of seniors to give them a better value for their health care dollar.”

The White House says 26 million people are already signed up for Plan D and are saving millions of dollars. The program has been described to seniors at more than 2,700 events across the country since January aimed at helping people get answers to their individual questions.

Bush spoke in the gymnasium of the Canandaigua Academy, the local public high school in this middle-class, conservative-leaning western New York community. Speaking to about 750 invited guests, Bush encouraged seniors to sign up for the prescription drug benefit. Joining him was Mark McClellan, chief administrator for the Centers for Medicare and Medicaid Services at the Department of Health and Human Services.

"I'm telling you, it's a good opportunity for you," the president said.

In a fact sheet, the White House said the federal government will spend an estimated 20 percent less overall on the Medicare prescription drug benefit in 2006 than was projected last July, a savings attributed to competition and wider availability of generic drugs.

The average premium for seniors for prescription drug coverage also is lower than projected — $25 instead of $37.

After the president's conversation on Medicare, Bush visited Ferris Hills at West Lake, a residence for seniors who are learning about Plan D.

"We're in your community to urge people to, you know, kind of step back, see what's available, design a program that meets your needs, if that's your interest, and it's going to save some money. That's the key," the president said.

Still, White House spokesman Scott McClellan conceded Tuesday that transition issues have been something of a problem. He said most of the obstacles have been found and fixed. He also noted that this is the most important benefit for low-income seniors in 40 years

McClellan earlier said seniors are realizing substantial savings on their prescription drugs. For a typical senior, the savings on prescriptions has equaled 50 percent or more of costs.

The political stakes are high in the debate over the drug benefit because older Americans are more consistent voters and are a larger share of the electorate, particularly in midterm elections.

Prior to the Medicare drug benefit's passage in Congress, Democrats favored an alternative approach with benefits provided directly by the government rather than through private companies. Democratic opponents now hope to seize on problems related to the implementation of the program through the airing of TV ads and by holding rallies to protest the program.

"You can have a private plan if you want, but if not, we want to provide Medicare Part D option for anyone to sign up for, where they know what the premium and the co-pay is, we negotiate group prices so you can get the best deal possible, go to your local pharmacy and get the medicine that you need," said Sen. Debbie Stabenow, D-Mich.

Democratic backers are trying either to force changes or make it a campaign issue this November. Americans United, a group with close ties to congressional Democrats, is already wrapping up its plan of attack on the new benefit.

"We believe that we can fan the smoldering embers of discontent ... into a firestorm of opposition," says a memo that sets out a strategy modeled on last year's successful drive to doom Bush's Social Security legislation.

While in New York, the president also met Jason McElwain, the autistic student and manager of the basketball team who scored 20 points in four minutes during a high school basketball game last month. His story was featured on national news.

"Our country was captivated by your amazing story on the basketball court. I think it's a story of Coach Johnson's willingness to give a person a chance. It's a story of Dave and Debbie's deep love for their son, and it's a story of a young man who found his touch on the basketball court, which in turn, touched the hearts of citizens all across the country," Bush told McElwain.

FOX News' Molly Henneberg and The Associated Press contributed to this report.