I am definitely Android biased as I'm not a fan of Apple's walled garden, or of being obliged to a single vendor. That said, Apple devices are nice and they seem to be the only company with a shipping tablet that is worth a damn; the augen gentouch78 Android tablet is nice, but you'd have to be delusional to prefer it over the iPad; it's desirable because it's cheap and hackable. Oh, and there are millions of iPhones and iPads out there so chances are rather good that one of your web properties will be rendered on one so it's probably worthwhile to take a peak.
Anyway, since Apple isn't getting my money, and I haven't convinced the PTB at the day job to acquire for me an iPad or iPhone with their hard earned cheddar, emulation will have to do and the iBBDemo2 from Blackbaud Labs seems to work well enough. The Blackbaud iPhone & iPad emulator an AIR2 app so you'll need to make sure your runtime is up to date, but it is relatively easy to operate (all AIR apps I have used have been easy to install) and it is good for checking mobile web sites in iDevices (at least the simple ones I have thrown at it thus for.
Though if any Apple product user out there wants to give it a whirl, it would be great to know how faithful the emulation is.
[UPDATE] Another handy emulator, though completely web-based, that includes the iPhone (among others), is offered by Cowemo. Called, amazingly enough, Mobile Phone Emulator, it includes emulation support for the iPhone 3GS, iPhone 4, HTC HD2, HTC Touch, LG U970, RIM Blackberry 8900 and the Samsung GT i5700
[UPDATE] Oops! It should really be "simulator" instead of "emulator". Sorry about that.