I just wanted to get my 2 cents in. I'm up here in Canada as well, on Rogers Wireless. I'm using just a normal mobile internet plan ($5) with a new unlocked Blackberry 8800.
I have an an application on my BB called Yahoo Go! that seems to work great with the generic data plan (BB came with it) -- it downloads my Yahoo e-mail flawlessly, and allows me to send back e-mail just as well. I know you're looking for Gmail, but some other e-mails do allow you to forward the e-mail over. It so happens to work out perfectly in my case. It's definitely not BB push e-mail, but for my casual uses, it's excellent.
For web browsing, you will need that BB plan, but using Yahoo Go! myself, I can bring up the news/entertainment/local weather/etc. so I can be forwarded off to a mobile website, and use their search function to bring up webpages, but I can't simply just insert a URL into the phone. So it's definitely limited there, but for my uses, it works wonderfully.
I was planning on doing a lot of texting, and with the Blackberry's keyboard and MSN Mobile, I'm also able to text message people on my MSN list using just SMS (pretty well all phones can do this, but the BB keyboard makes it oh-so-nice).
I know I'm not meeting all your needs there, but just something if you were wondering. This link has shown me pretty well everything I had needed to know: here
Cheers, and good luck -- let us know how it goes eh?