My favourite rifle scopes have been Leupold gold rings (Vari X III, VX-III, VX-3), but as I was able to afford higher end optics, I have also had good performance from Swarovski, Kahles, Trijicon, and Schmidt & Bender. Finally bought a couple scopes with illuminated reticles, and am looking at another.
For me, clarity, light transmission, eye relief, weight, ruggedness, reticle type and warranty are all important.
I prefer the duplex for a plain reticle, and really like the B&C and TDS/BRH reticles. Clean, simple and easy to use in the field.
Eye relief is important for those harder recoiling rifles. And lighter weight keeps them from wanting to come loose in the rings on the same rifles. (I do not use scopes with larger than 44mm objective lenses). Largest magnification I have owned to date is 3.5-18. Most are 3.5-10.
Leupold's lifetime warranty is a great feature that I have only used once, when I slipped and landed scope first on the rocks. Cost me postage one way, and had a repaired scope back on my rifle in 11 days with regular mail shipping both ways!
Have now used Swarovski warranty service twice:
Once to have my 19 year old SLC binos' eye cup repaired and checked over. They repaired and replaced most components for no charge, and I had it back in less than 3 months.
The other, there was something on the internal ocular lense only visible in bright sunlight against a white background (paper target). Paid shipping by mail one way. They replaced both ocular lenses, purged and tested the scope through a battery of tests and returned via mail to me in less than two months for no charge.
For binos, I can't say enough good things about my Swarovski SLC's! I also like my Leica Geovids 10x42 rangefinding binos. Was looking at the Swarovski EL Range 10x42's when I got a good deal on the Leica's and saved $1800.
I have an older Leupold 30x60 spotting scope, and when I get a higher end unit, it will be the Swarovski 20-60x60 spotting scope with angled eye piece. Side by side field comparisons beat out the Leica and Zeiss spotters of the same size for clarity, brightness and light transmission (at least to my eyes).