OK, so I've had a chance to (very quickly) scan through Yahoo! Go and read a bit more about it. The demo earlier this week was fairly impressive, but I wondered how it *felt*.
It seems a bit monolithic for my tastes - a 1.8mb native app is a significant download, particularly given that it's essentially a bundle of separate services: syncers for mail, calendars and photos and a load of bookmarks. There doesn't seem to be any syncing of news stories which seems like a missed opportunity: I already have an address book and calendar on my handset, but a news reader would be something *new*. This seems ideal to be broken down into separate apps - I'd be prepared to bet that most Yahoo! customers only use a few of all the available Yahoo! apps, but they're being treated as if they all use them all here.. Me? I don't use any Yahoo! services to any extent, and this app doesn't persuade me to. Now, if they gave me Flickr syncing, and used that to tease me into using other Yahoo! services, that might be more compelling. Shozu gets it right here, I think.
On some handsets, like the 6680, there seem to be problems. But the 6680 is pretty tight on memory for anything - Orange Homescreen + iSync zonked it out for me and made it unusable (with the camera only working 30% of the time), so I don't think we can blame Yahoo! for this. Perhaps they should warn 6680 owners though; this might be particularly pragmatic considering that for a while the 6680 was *the* handset for mobile/techie early adopters. For a more recent handset with more memory like the N70, Go seems a bit safer. I'm still very nervous about installing third party software onto my handset which alters how it works though (Yahoo! options pop up in my message reader now) - and keeps asking me about it. No, I don't want you to sync. No, I don't want a Yahoo! theme for my phone. Christian sees this integration as a feature; perhaps these concerns are just paranoia on my part.
Overall, Yahoo! Go seems rather niche. It's a nice stake in the ground for Yahoo! to demonstrate that they're taking mobile seriously, but practically speaking how many high-end Series 60-owning folks make use of so many Yahoo! services, want to use them when they're mobile, and want to pay for the privilege? We're back to the standard mobile problem of reach vs functionality, and this app is firmly wedged up at the functionality end of that curve. I'd be more impressed by a set of (perhaps simpler) apps which tease a significant chunk of Yahoo!s UK audience away from their desktops and onto their phones.
As an aside, I also find the use of proprietary protocols to do syncing confusing, when Yahoo! are simultaneously pushing their SyncML efforts elsewhere (which look great, though I've not tried them).
Christian's comment that the app will be preloaded onto S60 handsets is *very* interesting though... handset vendors and Yahoo joining forces to take on carriers? Hmm...