I'm glad to hear you're having success. Within the bounds of the techniques described in the flight manual (particularly those which are "limitations"), there is opportunity to fly any given aircraft with a variation of technique, depending upon your experience/comfort with the aircraft, and the situation.
Though I agree with those who posted that there is less drag, and therefore greater climb with the gear up, the difference can be smaller than one would expect, and getting to that lower drag configuration can involve busy hands, and temporary increases in drag. The Cardinal, like all 100 and 200 series (and 337) Cessna retractables will have a drag increase during retraction. The Cardinal is in the lesser affected group, with no main gear doors to open when you select "up", but you still have the affect of the main wheels turning sideways to the airflow for a number of seconds.
The 200 HP Cardinal RG has lots of oomph, so I would not worry about getting up and out (if you have to, you were into somewhere which as too tight). Remind yourself that the Cardinal started life as a 150 HP fixed gear, and then a 180 HP fixed gear. They were quite adequate aircraft.
A few other cautionary comments about the Cardinal; The very well maintained one I used to rent (wet for $55 per hour in 1978 - those were the days!), still had many failures to indicate gear position, due to switch problems. Prepare yourself for the day when you cannot confirm the nose gear is down. If there is an option for a mirror, I'd have it installed (if it's not already).
The flush fuel caps, though great on Lear jets, were not great on the Cardinal. The O rings on the caps tend to crack, and let in water, so be vigilant about draining sumps. More alarming is the fact that they can engage the filler with only two of the three tabs, and appear to be on when they are not. The difficulty in getting up to actually check them makes a visual confirmation for the rear tempting, but it's not enough. After the flying club fueled the one I used to rent, I visually checked it from the rear as taught - the caps looked fine. Fifteen minutes into my flight, I noticed that I was trailing a stream of fuel. I selected the tank with fuel left in it, to prevent further crossfeeding, and went right back. The cap was still in place, but I had siphoned out 45 gallons of fuel in about half an hour. Noticing that stream of fuel behind me was just luck. You're not really thinking to watch the fuel quantity fifteen minutes after taking off with full tanks! Left un-noticed, I would have been gliding before too long.
They are wonderful planes, and although a little different in feel to land, once you're used to them, they're great, even in short runways. I used to fly a 180 HP fixed gear Cardinal based at a 1600' grass runway, with wires at one end, and had no problems with short field performance.