Well technically, it is limited to 2500 images in a project, but that is unlikely ever to be an issue for what I need it for...Ah ok, I misread it, I thought the $99 option was still limited, actually pretty fair as it does seem to work very well. One question relating to the photomatch in Sketchup, have you ever have it do something weird if you are moving something while it does an autosave. Twice now it has changed the origin point in a weird way such that I have had to resort to a previous save.
Can't say I've seen any issues like that in SU. Although the way I work is that I only use it for referencing the photomatch. All moving/modelling is done in my other software.
I do find it to be quite a resource hog of the RAM though. For that reason, I tend to shut it down and restart at regualar intevals.
As I work on the primary model in other software not SU, what I ended up doing was just saving the SU with matched photos but no geometry.
Once I'd matched the photos, there was really no need. I added a reference line in SU (to the tip of the nose in my models case) and when importing my model, I'd use the line to position it. Once I'm done, I exit without saving. I also made sure to keep a backup copy of the SU file just in case!