i was thinking about the same. i spent the few extra bucks on the pro hd just because i can connect more to it. i've heard more bad reviews on the solo over the other sling products. if you don't mind spending the extra $ on family like me then i would go for the pro hd. its more modern. good luck though. i will test my international experience with my sling box for the first time in 2 months.
I'll take another approach to your question and say if your main use is for remote viewing and your streaming upload speed is below 2mb's, I'd say stick with the Solo. The picture quality out of the HD used remotely for a 2mb upload speed will have a picture quality improvement from nominal to marginal at best on an iphone or ipad compared to the solo; that is if you can get anywhere near that upload speed. Up the upload speed to 3 - 5 mb's and then the HD will become noticeable, but only through the slingplayer or slingcatcher. Problem is you rarely get those types of speeds out of the iphone / ipad. Benefits of the HD model, yes the extra tuner, but its not a deal breaker, and yes there have been certain issues (capacitors) with some solo's on the forum. Mine's lasted two years ( touch wood ) and contines to work fine which I also use with an iphone. I believe keeping it running in a cool place has extended the slingbox's life, so its your call. What you're dealing with is the question of whether to double the hardware cost for remote viewing that won't see that much of a picture improvement on an iphone or ipad even if you've got a 5mb upload connection, because you won't get anywhere near that with the ipad. Your last comment was "if it truly would be that much better". I don't think those type of picture improvements would apply in comparion to the HD from the Solo for what you'll be using it for. Just don't expect netflix streaming quality out of the slingbox through the ipad whether you choose the solo or HD.