ISRG sells and services the patented da Vinci robotic surgical system supporting doctors in minimally invasive surgery (MIS) for an expanding array of procedures. Yesterday we were informed that the installed base of da Vinci Surgical Systems has grown from 559 at December 31, 2006 to 1,111 at December 31, 2008 to 1,242 at June 30, 2009.

I was happily greeted in the morning with an email that started off "Way to go dude. 29 point pop in ISRG today." That was only for starters; ISRG closed yesterday at $215 up $45.58 gaining 26.84%!

My popular colleague Jim Cramer and I have not seen ISRG under the same light the past few months. While I made ISRG one of my 2009 stock picks, last reviewed in Chasing Value: 2009 picks 731% better than S&P -- 2nd quarter review , Jim has held a contrasting view and offered this on June 5 as reported by Sung Moss of TheStreet.com:

• The stock is up 81% since March, but Cramer said good times are coming to an end. The company makes a robotic surgical system called da Vinci, which is used on hysterectomies and prostate surgeries.But Cramer said the company may be running out of customers. A quick survey of the hospital sector will tell you that the industry is hurting under mounting debt loads. Simply put: customers for da Vinci just can't afford it right now, meaning that he expects sales to plummet

I thought hard about my rather heavy position in ISRG after Cramer's dissing the stock. After all, it is true that it had made a powerful gain and the economy had plenty of uncertainty left in it, and still does today. But given the stock's unique product and undisturbed monopoly I held fast. If I had not I would have certainly been disappointed in myself.

Today the stock is up another $6.00 topping $121 at 2:00 PM EST. I have trimmed a few shares taking some profits, however, Intuitive remains one of my largest holdings and will remain so for the foreseeable future.

Given its rapid rise and the unpredictability of the market anyone interested in buying into the stock now might consider doing so in baby steps. If you buy a few shares and it continues to gain value then you will be delighted. If it goes down you will have some cash to buy more, dollar cost averaging it, while you build a position.

I did this myself over the past ten months and reported on it in April Chasing Value: Intuitive Surgical's right price.

If you are interested in my original recommendations from last December you can read Chasing Value: 9 picks for 2009 -- APC, GE, ISRG, WFC and more

Update: ISRG closed at $222.53, up $7.16 or 3.32% for the day.

Sheldon Liber is the CEO of a small private investment company and the principal for design and research at an architecture & planning firm. He writes the columns Chasing Value and Serious Money. Disclosure: I own shares of ISRG.