Without knowing the reference ranges for those metrics I've no idea if they're impressive. Are you able to provide any context here?
Ueli Steck running up and down mountains, including his Himalayan exploits last year, are pretty impressive feats of fitness.
Context sure:
Killian's VO2 max of 90ml / kg / min:VO2 max (widely accepted as the single best measure of cardiovascular fitness and max aerobic power). Average untrained healthy male will have a VO2 max of approximately 35-40 ml/kg/min.
Elite male runners can consume up to 85 ml/kg/min, and female elite runners can consume about 77 ml/kg/min. 5 time Tour de France winner Miguel Indurain had a VO2 max of 88.0 at his peak.
His results speak for themselves though really:
Mountain Running:2009:
1st, Skyrunner World Series
1st, Mt. Kinabalu Climbathon
1st, Ultra Trail Andorra
1st, Ultra-Trail du Mont-Blanc
2010:
1st, Sierre-Zinal "La course des cinq 4000" 31 km
1st, Grand Raid de la Réunion
World Record, Mount Kilimanjaro, Ascent and combined Ascent/Descent (5:23:50, 7:14:00)
2011:
1st, The North Face 100, Blue Mountains, Australia. Course Record
1st, Western States Endurance Run
1st, Ultra-Trail du Mont-Blanc
Ski Mountaineering:2010:
1st, World Championship vertical race
1st, Trophée des Gastlosen (ISMF World Cup),
2nd, World Championship single race
3rd, World Championship combination ranking
2011:
1st, World Championship single race
1st, World Championship vertical race
1st, World Championship vertical, combined ranking
4th, World Championship.
1st, Mountain Attack
2012:
1st, European Championship vertical race
1st, World Championship vertical, combined ranking
2nd, European Championship single
1st and course record, Mountain Attack
1st, Patrouille de la Maya.
But perhaps most impressive of all is his recent move into alpinsm:
On 18 September 2012, Kilian ascended from Courmayeur to the summit of Mont Blanc via the famous Innominata Ridge (1000m, D+, V+, 60º) in 6 hours and 17 minutes. He then raced down to Chamonix in a total time of 8 hours 42 minutes. (Average time for a fit team is circa. 3 days).
Ueli Steck's comment on Killian's move into alpinism: "Can you imagine what I could do if I had the fitness and physique of Kilian?"