My wife and I chose to cruise with Celebrity on our 1st time cruise after doing as much research as we could (and working with our travel agent). At the end, we narrowed it down to Princess and Celebrity and opted to go with Celebrity as we liked the itinerary better. We were a little adventurous for 1st time cruisers as we picked a 14 day cruise as our inaugural voyage but we were glad that we did.
Overall we had a wonderful time and met some wonderful people.
We met a couple from Ontario, Canada (we are from Alberta, Canada) while waiting in the lounge prior to embarkation. They are avid cruisers and had cruised on the Equinox (sister ship to the Eclipse) so they knew where everything was and offered to show us around once we boarded. This chance encounter had a huge positive influence on our cruise as we ended up spending a lot of time together. The remarkable thing about that is that my wife and I are in our late 30's and they were in their late 50's and early 60's.