I wouldn't call the Piezoelectric ignition particularly reliable but I have yet not had to resort to a lighter, Lucifer stick or firesteel to get the el cheapo Gelert Blaze PZ micro stove to take hold. The trick it seems is to get the stove to fire up is by adjusting the gas regulator to a very low output setting, then a quick few short stabs of the piezo button.

Above 7000 feet you may well need to resort to a firesteel or Lucifer stick. The advantage of the Piezo ignition is it just simply there, attached to the stove. If it doesn't work then you have to start looking in your pockets for the firesteel or non piezo ignition lighter (even a Zippo BLU lighter doesn't cut it to reliably fire up a gas cartridge stove) etc to get the stove to fire up.

Edit ----I have just ran a quick test to see how the el cheapo Gelert Ti stove performs. Piezo ignited first time.

I used a 1 litre Etapower pot this time indoors. Here are the stats;

300ml of water - Just enough for a large mug of Ovaltine.
Water temperature about 14C
No wind
Ambient temperature around 22C
Time to bring to a rolling boil - 1min 20sec
Fuel used = 3-3.5 grams of fuel.

Total projected water to bring to rolling boil for 100gms gas canister = approx 8-9 litres of water in favorable conditions.