Yes, Pixelan is excellent for luminance transitions. ProDAD Adorage is another excellent plug-in that will keep you busy with transitions for quite a while.
I have ProDAD Adorage and like it. Gives me some interesting transitions. However, there is nothing like the standard disolve and fade to black :-) I also like wipes. Loved them since the original Star Wars.
Aside from the transitions mentioned here, it's VERY easy to make your own. Plus, ArtBeats has a great transitions library that works well for Vegas among other NLE's.
How to include Adorage in Vegas Video ?
After the installation "Adorage All Plugins Pack" of course all older volumes with its effects are being included in the plugin ready to be used in Vegas Video. Description:
VEGAS Video Plugin
1. Create a transition effect for 2 video streams in the Vegas timeline as you´re doing it usually with the Vegas included effects.
2. From the transition effect list drag the icon "proDAD Adorage" onto the transition area in the timeline.
Adorage opens and the preview with standard video signals appears.
A preview incl. the timeline video signals can be shown by playback the timeline during editing the Adorage effect.
In Adorage made changes will be shown interactive in the Vegas preview.