[Arkcon]

To summarize even more -- stealth armor is cheap and common, for either the A.I. or people on PBW. If you don't get level 1 sensors up and running, you'll regret it sooner, not later.

The higher level sensors let you see what's happening in nebulas. If one borders your space, they're a good place to see an incoming enemy fleet. You can build fighter bases and ship yard bases and use them against the fleet if you can see it. If the nebula also disrupts shielding, fighter Groups can really rip though those shielded dreadnoughts and stall the fleet.

The cloaking device gives higher cloak levels, but it takes much less research to get level 3 sensors than to get a level 3 cloaking device. So its not a real show stopper. You might get lucky.