I have a couple Toshiba XS32's which were also "stuck" on the incorrect black level settings (and went WAY up the chain at Toshiba complaining about this, who vehemently denied there was ANY problem, but they sure made sure to have a brightness level settings on all future models of the XS recorders!) and the +7.5IRE IS noticeable, but mostly on very dark scenes. It's one of those problems that the more you are aware of it, the more you will notice it. Until the problems became apparent (thanks to reading this site
) I had no idea the XS32s had a problem. (although at the time my DVD players were set to "darker" modes which masked the problem)
(and Toshiba had a cute little trick of video recorded onto the XS32's hard drive was played back at the correct IRE level [it went into a "darker" mode] but then when burned on DVD it didn't compensate... so they obviously KNEW at some engineering level that the IRE levels were wrong, but didn't care enough to fix the issue on the produced DVDs)
Now that I have an HDTV (and a DVD's player "darker/lighter" settings don't usually have any sway over HDMI) many of the DVDs I recorded with the XS32 are definitely noticeably light; it's frustrating but not quite to the point that I have re-recorded anything, although I've been tempted to a few times. (especially for things like my copies of laserdiscs that were never released on DVD) It's on the list of "things to do when I have spare time", which unfortunately the list only seems to get longer and longer...!
When you really have a problem is when you give a DVD to a friend who, for whatever reason, has their set's brightness levels waaaay too artificially high; then the DVDs look very washed out. Of course there's a bigger issue there with the set calibration, but I've had some people notice the DVDs I gave them were VERY light (often people who watched them on a very bright computer screen).
Shorter version: if you notice it will really depend on your eyes, how nitpicky you are, how your playback sets are calibrated, and the content you're playing. Until you try to test it it's hard to describe.