I wouldn't be so quick to write off E (scratch that... PLEASE, everyone, disregard E. Leave them alone. They're "outdated" ... You're better off building on a trendy web2 name... )
While I is definitely trending pretty strong for new-agey branding (and I do own several of them and love each one like a child), E is old-school, internet bedrock. I recently caught eNapkins.com off drop (which I was positively ****ing thrilled- go look at the keyword verts for "Napkins"...) - I would prefer eNapkins to iNapkins. I cannot articulate why that is, but I'm pretty sure my instincts are right. If I had to choose between eDormroom and iDormroom, I would probably go I, given the target demographic. Again, I cannot articulate exactly "why" beyond demographic considerations, but I'm confident in this.
Also, I think people err when they take the whole "e is for electronic, i is for internet" thing too literally and use that in their decision making process. The cornerstone of the prefix concept is branding. Period. While it had a stream of logic in the early days, today, prefixing is a simple way to have a brandable name platform while remaining as succinct as possible while being entirely keyword lucid. If you're selling to the masses, they recognize a prefixed keyword as a brand. They don't deconstruct the meaning behind the prefix itself- hell, I'd bet less than 1/100 people even know the difference.
Anyway, yeah. Prefixes bolted onto nice, commercially viable keywords and in .com. Huzzah huzzah. They're basically viable, pre-branded businesses you can buy for a few dollars. But shhhhhhhh..... Don't tell anyone. Let them keep buying what they're buying :D