I joined PBase in June 06 after using a cheapo site for a few years - It's been great. I like the layouts, and as others said I liked that it felt more presentable and 'professional'. It's very easy to do uploads (drop them in a .zip folder and upload any number of pictures at once)...no limits on resolution or file size, allows linking and posting without limits, you can sell if you want, make some galleries private and others public, etc. They are currently selling blocks of 500MB for $23 a year, which is in line with most other sites, with the flexibility to use that 500MB however you want (more pics at smaller res, less pics at higher res).
I've got nearly 1,400 photos on my site, separated into 31 galleries and sub-galleries - with no problems so far.