Allow me to elaborate a little more here.
The problems I'm having really stem from the new HD interface, but it can be turned off (which I have done until they get it worked out). Essentially, I'm left with a Series 3 Tivo (or TIvoHD) with a faster processor and larger hard drive. The SD UI is nearly identical to the S3 UI, only with a faster processor.
So if you have a Series 2 Tivo, like it and want to record in HD then by all means, upgrade to a Premiere (and you should do so through Tivo.com for a discount - I upgraded a series 2 for about $220). Just be prepared to turn off the HD UI.
If you have a Series 3/TivoHD and like it, then the only reason why you would want to upgrade is because you find it too laggy or you need/want more recording space (and you should do so through Tivo.com for a discount).
If you have a cable co DVR and want to replace it with a TiVo, then by all means grab a premiere. It's still cheaper than the Series 3 when it came out and is more powerful. Just be prepared to turn off the HD UI.
This thing will get better, but if you're buying it for all the cool stuff TiVo showed off at the big press conference, forget about it for at least a month, and I don't think I'm making a stretch here when I say wait 3 months.
And special note to Julian - you should buy a new one through Tivo.com to get the discount. They even offered me the ability to keep my exisiting TiVo for $10 a month and add the Premiere so an "upgrade" should be read as "add additional." I saved about $70 on the first Premiere vs the retail price I paid for the second one at Best Buy, plus $3 off the monthly service.